1. Field of the Invention
The present invention relates to a lens barrel for fixably or movably holding a plurality of lenses, a method of adjusting the lenses supported on the lens barrel, and an imaging apparatus including the lens barrel, and relates particularly to a lens barrel, a method of adjusting the tilt of a lens and an imaging apparatus in which the tilt of a lens holding members for holding a lens group may easily be adjusted.
2. Description of the Related Art
In recent years, imaging apparatuses represented by cameras, such as a digital video camera and a digital still camera having a solid-state imaging apparatus, such as a CCD (charge-coupled device) and a CMOS (complementary metal-oxide semiconductor), have increased the number of pixels due to an increased integration of the solid-state imaging apparatus. In addition, an optical system for an imaging apparatus is expected to include higher resolution, a lens barrel with a reduced size, and increased magnification of the zoom ratio.
Accuracy in an optical system and a mechanism system may be necessary for realizing a high resolution of the optical system along with reducing the size of the lens barrel; in particular, accurate lens eccentricity may be increased.
On the other hand, magnification of the zoom ratio may be achieved by increasing the number of operation strokes or increasing the refractivity of a lens group that determines a zoom magnification. However, increasing the number of operation strokes of the lens group contradicts the decrease in the size of the lens barrel, and the lens group may be adjusted more strictly and accurately when increasing the refractivity of the lens group. The eccentricity of the lens is frequently adjusted in an imaging apparatus, such as a digital video camera and a digital still camera. A step of adjusting the eccentricity involves drawbacks from a viewpoint of cost effectiveness and number of steps. Accordingly, it is desirable that the lens eccentricity be easy and simple to adjust in the imaging apparatus.
Further, the imaging apparatus represented by the digital video camera and the digital still camera mostly implies that consumer camera products and their value as camera products may not increase without improving the reliability and safety of camera products. In particular, with regard to the reliability of camera products on the market, various types and applications of a camera may be expected in order to satisfy the requirement for high reliability. Accordingly, the imaging apparatus represented by the digital video camera and the digital still camera may have a configuration capable of maintaining a sufficiently high reliability. If the lens barrel of the imaging apparatus is reduced in size by employing a simple mechanism, some defects may appear on the market after shipping the products. This factor may impose restrictions on the adjustment of the lens eccentricity in view of the mechanism, thereby restricting the reduction in size of the imaging apparatus and increasing the number of steps.
Japanese Unexamined Patent Publication No. 2003-43328 discloses a lens barrel according to the related art and, more particularly, describes a method of adjusting a zoom lens, a method of adjusting an imaging apparatus including the zoom lens and a zoom lens and an imaging apparatus adjusted by these methods. According to Japanese Unexamined Patent Publication No. 2003-43328, the zoom lens described is characterized in that the zoom lens includes a stationary lens group and a movable lens group. The zoom lens includes a movable lens group that moves in an optical axis direction to adjust a focal length and a focus. In the zoom lens, the tilt of the stationary lens group may be adjusted relative to the optical axis such that image formation is measured at four or more measuring points on the formed image, defocusing coordinates with which the best image formation is obtained at the respective measuring points are specified, four or more planes formed by three points of the specified defocusing coordinates are defined, the tilt of the stationary lens group is figured out when having four or more planes matched by adjusting the tilt relative to the optical axis of the stationary lens group, and the calculated tilt of the stationary lens group relative to the optical axis is used as a target point of the adjustment.
According to the zoom lens having the above-mentioned configuration, “a tilt of a lens can easily be adjusted without consuming time and labor for replacement of adjustment parts and without displacing the position of the center of the lens center in the optical axis direction” (paragraph [0104] in the patent specification).
Japanese Unexamined Patent Publication No. 2004-163865 discloses another example of the lens barrel according to the related art and, more specifically, discloses a lens alignment mechanism for aligning a lens when a lens holding member for holding the lens is attached to a lens barrel body, a lens apparatus and an imaging apparatus including such lens alignment mechanism. The lens apparatus described in Japanese Unexamined Patent Publication No. 2004-163865 is characterized in that “the lens apparatus includes a plurality of lenses for focusing a subject image, lens holding members for holding at least one of a plurality of lenses, and a lens barrel body to which the lens holding members are attached. In the lens apparatus are located a plurality of lenses such that the optical axes of the lenses agree with each other, a supporting device for properly positioning the lens holding members relative to the lens barrel body within a plane perpendicular to the optical axis of the above-described lens, supporting the lens holding members such that the lens holding members may move in the optical axis direction, and a plurality of adjusting members rotatably attached to at least three portions of the outer peripheral surface of the lens barrel body, in which tilts of the lenses held by the lens holding members may be adjusted by rotating the respective adjusting members to displace the lens holding members in the optical axis direction.
According to the lens apparatus having the above-mentioned configuration, the lens alignment mechanism may be reduced in size as compared with the size of the related-art lens alignment mechanism, and expansion of the outer form of the lens barrel body may be minimized so that the entire size of the lens apparatus and the imaging apparatus including such lens alignment mechanism may be reduced in size (paragraph [0107] of the patent specification) can be achieved.
However, the zoom lens disclosed in the Japanese Unexamined Patent Publication No. 2003-43328 has encountered the following drawbacks. In a step of adjusting tilt eccentricity (adjustment item in the large magnification) of a first lens group, first, the first lens group is located at a designed target position using a position adjusting mechanism including a pressure spring and a drawing screw for presetting the height and the tilt in the optical axis direction. The target position is determined using a statistical central value computed by the feed-back obtained from a formed image at four measuring points within the focusing plane in the next step, and the target value is changed when the position of a metal mold is modified. As a result, management of the preset step and the measurement step becomes complicated such that more work steps may be required.
In the lens apparatus disclosed in the Japanese Unexamined Patent Publication No. 2003-43328, the lens holding members are elastically supported on the lens barrel body using the supporting devices provided at the three portions and tilts of the lenses held on the lens holding members are adjusted by using the adjusting members provided at the three portions. Specifically, the supporting points of the three portions to support the lens holding members are respectively the movable floating supporting points so that, if the supporting point of one portion is adjusted, such adjustment of one supporting point affects the other supporting points of two portions, thereby causing a reference point (position) to change constantly. Therefore, problems arise in which an adjustment work becomes complex and in which it is difficult to adjust lens tilts to the desired states.